Many food products are comprised of more than one part where one part needs to be moist and another part needs to be dry in comparison. For example, foods having a pastry crust and a moist filling often need to have some form of layer of moisture resistant material between the pastry and the filling. In the absence of such a moisture resistant layer, the pastry may become too moist and soggy, and therefore unappealing to a consumer. Other examples of products requiring a moisture barrier include pies, pizzas, snacks, wraps, sandwiches, croque-monsieur, and many others.
Moisture barriers for use in food products are known. They are typically hydrophobic films. But most hydrophobic films suffer from significant drawbacks. There is currently no acceptable hydrophobic film for use as a moisture barrier in food products that are prepared by baking or similar heat treatment. Those barriers that are heat stable tend to have negative sensory properties, meaning that they leave a waxy coating in the mouth which is undesirable to many consumers. They have limited efficiency because the use of high temperature melting fats and waxes usually means that plasticisers are required to simplify the application of the fats or waxes and to avoid the formation of cracks in the barrier. Existing heat stable barriers typically have poor nutritional properties, particularly due to the levels of saturated and trans fatty acids in high temperature melting fats and waxes. Moreover, there are often regulatory restrictions on the application of some barrier materials (e.g. shellac).
Emulsified materials can be used as moisture barriers in food applications. For example, EP 0471558 describes an emulsion comprising lipid (74 to 95%) and a biopolymer emulsifier (5 to 26%). However, this high level of biopolymer is detrimental to the efficiency of the barrier. The more hydrophilic the material, the lower the efficiency of moisture migration prevention. More importantly, a film prepared from this emulsion encloses dispersed oil droplets and forms a continuous network of non-hydrophobic materials which therefore allows moisture migration through the film.
U.S. Pat. No. 5,543,164 also describes a moisture barrier prepared from an emulsified material. But again, the continuous matrix of biopolymer as well as the high level of biopolymer (5 to 20% protein) leads to a barrier that is not particularly effective.
U.S. Pat. No. 4,293,572 describes an emulsion that is applied to a food after baking or frying for the purpose of preventing moisture migration. The product must be cooled to below 40° C., clearly showing that this barrier is not heat stable. In other words, the barrier cannot be applied prior to cooking or baking of the food product.
There is therefore an ongoing need for a heat stable hydrophobic film for use in multi-component food products.
The applicant has now found that an emulsion of a lipid and a biopolymer emulsifier can form a heat stable hydrophobic film and is an effective moisture barrier in food products.
It is therefore an object of the invention to provide a food product incorporating a heat stable moisture barrier, or to at least provide a useful alternative.